The invention relates to a cleaning/washing composition comprising a non-toxic and safe system of immiscible liquids with high interfacial tension which does not require the use of additional detergency benefit agents, and to an improved process/method of cleaning/washing fabric using the same.
Conventionally, fabric is cleaned using water and a detergent surfactant system which is known as wet cleaning. Surfactants adsorb on both fabric and soil and thereby reduce the respective interfacial energies and this facilitates removal of soil from the fabric. Alternatively, it is done by a process called dry cleaning where in organic solvents such as perchloroethylene (PCE), petroleum based or Stoddard solvents, chlorofluorocarbon (CFC)-113 and 1,1,1-trichloroethane are used, all of which are generally aided by a surfactant. The organic solvent helps in the removal of oily soil in the presence of detergents. Soil removal can be achieved by a small reduction in interfacial tension. The particulate soil is largely removed by providing agitation.
The organic solvents used for cleaning are generally toxic and also pose a problem as they are inflammable, creating potential fire hazards. Another major concern in solvent cleaning is the tendency of vapour loss from the cleaning system into the atmosphere especially when they are used at elevated temperatures. Solvent cleaning processes generally employ chlorinated solvents that are linked to ozone depletion. Several attempts have been made to avoid these problems and to find suitable substitutes.
WO-A-0036206 (3M) discloses dry cleaning compositions comprising hydrofluoroethers along with other co-solvents, and water present in an amount of less than 1% by weight of the composition. Hydrofluoroethers are relatively safe and less aggressive towards fabric.
U.S. Pat. No. 6,228,826 (MiCell Tech. Inc.,), discloses the use of end-functionalized polysiloxane surfactants to enhance the dry-cleaning aspects of carbon dioxide which was earlier considered as an alternative to the potentially toxic halocarbon solvents.
Regardless of the type of solvent used, which may be water or organic, agitation of garments in the cleaning medium is essential to accelerate the removal of the soluble soil or the insoluble, particulate soil. During dry cleaning when a surfactant is used, a maximum of about 10% of water is also used along with the solvent system in order to facilitate the removal of water soluble stains.
Our earlier-filed co-pending application WO-A-01/90474, published on Nov. 29, 2001, discloses a process of cleaning fabric using the liquidxe2x80x94liquid interface of at least two immiscible liquid phases with an interfacial tension greater than 5 mN/m, under agitation. Even in this method of cleaning the solvents used could be toxic, inflammable and have an impact on the environment.
It has now been found that if in the above-mentioned immiscible liquid phase the less polar solvent has a carbon chain length of at least 4 or is a silicone with more than 3 SiO units the above mentioned problems of toxicity, flammability, and environmental impact can be circumvented whilst retaining superior cleaning of fabric. The system comprising the immiscible liquid phase is superior to pure solvent cleaning in terms of the detergency benefit, especially for particulate soil. The carbon chain length should preferably be greater than 6.
The applicants have found that efficient removal of both soluble and insoluble soils may be achieved by the cleaning of fabric under agitation using a washing/cleaning system comprising a liquidxe2x80x94liquid interface of at least two immiscible liquid phases with an interfacial tension greater than 5 mN/m, wherein the less polar solvent has a carbon chain length of at least 4, or is a silicone with more than 3 SiO units. It is also found that superior cleaning may be achieved economically by the use of water as a major component along with the organic solvent with the use of little or no surfactant contrary to prior art which teaches use of water at levels not exceeding 10% together with the use of surfactants.
The applicants have developed a system with at least one immiscible phase and with high interfacial tension which provides superior cleaning.
Thus according to one aspect of the present invention there is provided a cleaning/washing composition comprising an immiscible liquid system having an interfacial tension greater than 5 mN/m wherein the less polar solvent has a carbon chain length of at least 4 or is a silicone with more than 3 SiO units.
Interfacial tension may be measured using various techniques, such as sessile drop, pendant drop, spinning drop, drop volume or Wilhelmy plate method. For the purposes of the present invention, interfacial tension is measured by the Wilhelmy plate method, using a Kruss Processor Tensiometer K12, at 25xc2x0 C.
For some systems, the interfacial tension may change whilst undergoing shearing forces typically encountered in a wash process. It is customary to refer to the interfacial tension under these conditions as a xe2x80x9cdynamic interfacial tensionxe2x80x9d (DIFT) and may be measured by a maximum bubble pressure technique.
According to a preferred aspect the cleaning/washing composition comprises an immiscible liquid system with an interfacial tension greater than 10 mN/m, wherein the less polar solvent has a carbon chain length of at least 4 or is a silicone with more than 3 SiO units and the concentration of the most polar liquid is 10-90% (v/v).
According to a more preferred aspect of the present invention the cleaning/washing composition comprises an immiscible liquid system with an interfacial tension greater than 20 mN/m wherein the less polar solvent has a carbon chain length of at least 4 or is a silicone with more than 3 SiO units and selectively provided such that the concentration of the most polar liquid is 40-90% (v/v) for a period of at least 5 minutes during the wash process.
It is preferred that the carbon chain length of the less polar solvent is greater than 6, particularly greater than 12 and more preferably greater than 16.
According to another aspect of the present invention there is provided a process of cleaning fabric comprising agitating the fabric in the above disclosed immiscible liquid system having an interfacial tension greater than 5 mN/m, wherein the less polar solvent has a carbon chain length of at least 4 or is a silicone with more than 3 SiO units.
Solvents
The less polar solvents that have a carbon chain length of at least 4, preferably greater than 6 may be selected from branched and linear alkanes (chemical formula CnH2n+2 where n is at least 4, preferably greater than 6), including but not limited to hexane, heptane, octane, nonane, decane, dodecance, tridecane, tetradecane, pentadecane etc. and mixtures thereof. Commercially available mixtures of this type include Isopar L (C11-C15 alkanesxe2x80x94ex Exxon) and DF2000 (C11-C15 iso-alkanes; CAS #90622-58-5, ex Exxon). They may also be selected from branched and linear alkenes with at least 4, preferably more than 6 carbon atoms including but not limited to octenes, nonenes, decenes, undecenes, dodecenes etc, with one or more double bonds, and mixtures thereof.
They may also be selected from ethers with at least 4 carbon atoms including fluoroethers such as methoxy nonafluorobutane HFE-7100(i.e. C4F9-OCH3) and ethoxy nonafluorobutane HFE-7200(i.e. C4F9-OC2H5); from esters with at least 4 carbon atoms, such as dibutyl phthalate, dioctyl phthalate, C8-C24 saturated and/or unsaturated fatty acid methyl esters; and terpenes such as limonene; and mixtures of the above.
C8-C24 saturated and/or unsaturated fatty acid methyl esters are particularly preferred esters as less polar solvents, and typical examples thereof are C10-C18 fatty acid methyl esters such as methyl laurate, methyl myristate, methyl stearate, methyl linoleate, methyl linolenate and mixtures thereof.
The less polar solvents with more than 3 SiO units may be selected from polydimethyl siloxane oils. Linear and cyclic siloxanes known as Lx and Dx where x is greater than three are suitable for use in the invention. Specific examples include octamethylcyclotetrasiloxane (D4) (ex-Dow Corning), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), decamethyltetrasiloxane (L4) and dodecamethylpentasiloxane (L5).
The immiscible liquid system furthermore comprises at least one other, more polar solvent such that the liquid system has an interfacial tension greater than 5 mN/m. Such more polar solvent may be selected from water, alcohols, ketones, aromatic solvents, halogenated solvents, heterocyclic compounds; and hydrocarbons, paraffins, esters, and ethers with less than 4 carbon atoms. Preferably the more polar solvent is water.
It is possible to incorporate other conventional detergent ingredients such as surfactants, builders, anti-redeposition agents, soil release polymers, hydrotropes, enzymes, bleaches, fluorescers, perfumes etc. into the immiscible liquid system.
Agitation
Agitation can be provided by impellers that cover the vertical flow profile or radial flow profile or a combination of both so that thorough mixing of the immiscible liquids take place. Agitation can be provided by impellers that are open curved turbine, turbine type propeller, axial flow turbine, flat blade turbine, inverted vane turbine, marine propeller etc. This action may also be accompanied by a tumbling action. Optionally agitation can also be provided by a combination of rotation and tumbling action. Other forms of agitation using gas jets or ultra sound may also be employed. Other forms of agitation generally known in the art can also be employed provided it ensures a good mixing of the immiscible liquid phases.
The nature of the invention, its objects and advantages will be more apparent from the ensuing description made with relation to non-limiting exemplary examples of the above identified various aspects of the invention.
The invention will now be described in greater detail with reference to immiscible liquid compositions for cleaning fabric.